This invention relates to large screen displays for presenting images to a number of viewers. More particularly this invention concerns a large screen display capable of operating in real-time at high resolution rates and the presentation of video information. In still greater particularity this invention provides for an electronic driven acousto-optic modulation of a coherent beam and its acousto-optic deflection in the X-direction and Y-direction to enable higher resolution portrayal of information at video rates on a remote screen.
The advantage of presenting information to a large group of viewers on a screen has long been appreciated. Educators and managers frequently use such displays when getting their point across. A noteworthy advance in this field is the display that was referenced above. Its use of the liquid crystal light valve to modulate the high intensity lamp to project the high-resolution image to the screen represents a need long felt in the art. The improved resolution afforded by its modulated coherent writing beam and the responsiveness of the liquid crystal light valve to modulate the incoherent light projection beam were largely responsible for its improved capability; however, the mechanical scanning arrangement shows disadvantages such as mirror facet errors, mechanical wobble, and realignment because of bearing wear and introduces limitations with respect to the resolution and the rate at which an effective presentation could be made.
Several approaches for displaying information have been developed, among them being: U.S. Pat. No. 3,514,534 has a laser TV display system using Acousto-optic Bragg cells for both the laser modulator and for the horizontal deflector; but, for the vertical deflector a mechanical deflector is used to direct the beam onto a screen. U.S. Pat. No. 3,723,651 shows a laser beam modulated by a video signal and deflected by x and y deflectors to form an image on a transmissive liquid crystal light valve. The liquid crystal used operates in a transmissive dynamic scattering mode and used a flashlamp to alternately project the image then erasure of liquid crystal image at 60 images per second. The x and y deflector components are not identified. Another U.S. Pat. No. 3,727,001 has a real-time, two-dimensional imaging apparatus employing laser scanning of an acousto-optic array of elements and r.f. driven signals to convert an acoustic image pattern into a visual display. The U.S. Pat. No. 3,818,129 discloses a direct laser imaging device (no light valves) including beam shaping optics, laser modulators, laser projection optics, and employing more than one laser source to produce color displays. Another U.S. Pat. No. 3,894,182 provides a picture display device intensity modulating a light beam by a video signal and a light receiving surface is scanned employing mechanically driven mirrors. Still another U.S. Pat. No. 4,295,159 has a real time display device using a CRT driven liquid crystal light valve and associated projection optics.
Thus, there is a continuing need in the state-of-the-art for an all-solid-state optical scanning device with no mechanical moving parts device for stability and reliability of operation a high resolution in the neighborhood of 2,000 lines or higher at video scan rates to more effectively display information on a wide screen.